The present invention relates to the production of ternary or quaternary semiconductors from a solvent zone, and more specifically to the improvement, in the specific case of the compounds Cd.sub.x Hg.sub.0.5-x Te.sub.0.5 and Cd.sub.x Hg.sub.0.5-x Te.sub.y Se.sub.0.5-y (0&lt;x&lt;0.5;0&lt;y&lt;0.5), of the method described in French Pat. EN No. 744 2769, filed on Dec. 24, 1984 by the Commissariat a l'Energie Atomique.
The aforementioned method consists of passing through a solvent zone at a specific temperature contiguous bars of elements or alloys of elements thereby bringing about the synthesis and crystallization of composite semiconductors.
The aforementioned known method is illustrated in FIG. 1, which shows two ingots A and B corresponding to one of the constituent compounds of the semiconductor formed.
In FIG. 1 this drawing, the two ingots A and B forming the bar are cylindrical, have the same diameter and are laterally truncated along face 2 and are joined by the same face. The assembly of said two ingots A and B is introduced into a cylindrical quartz weighing scoop 6 in the vertical position and is passed through an induction furnace 13, within which there is formed a solvent zone 8, previously placed at the end of the scoop at which crystallization starts and The induction furnace 13 heats the scoop portion passing therethrough and its contents in the portion facing the furnace. Scoop 6 moves in the direction of arrow 14 through the annular space defined by the furnace. After passage through the furncace, the contents of the scoop portion crystallize, forming zone 10.
During growth, it is possible to successively observe zone 10 in which crystal AB is located, crystallization interface 12, solvent zone 8, dissolving interface 15 and a reaction starting area 16, where the compounds are in a close to stoichiometric proportion with a view to the formation of crystal AB.
From a general standpoint, the use of a solvent makes it possible to produce composite semiconductors at a temperature below the melting temperature thereof, and consequently to obtain materials which are purer and have a better crystalline quality. Specifically, the use of a solvent in the case of compounds Cd Hg Te and Cd Hg Te Se also makes it possible to obtain independence from the high mercury vapor pressures at the melting temperatures of these compounds.
The production process described in patent EN 7442769 meets the aforementioned general and special conditions, but is difficult to perform in the case of producing Cd Hg Te or Cd Hg Te Se.
Thus, the dissolving by means of the solvent (in this specific case either tellurium, or liquids Hg.sub.y Te.sub.z or Cd.sub.x Hg.sub.y Te.sub.z with z&gt;0.5 and x+y+z=1) of the two bars of alloys Cd Te and Hg Te for the ternary compound Se and Cd Te and Hg Te or Cd Te and Hg Te Se for the quaternary compound preferably takes place on the mercury chalcogenide, thus placing the solvent zone outside the thermodynamic equilibrium. In the use of the solvent (Hg.sub.y Te.sub.z or Cd.sub.x Hg.sub.y Te.sub.z), z is higher than 0.5, i.e. in excess and mixtures and not compounds are involved. The ternary or quaternary composite semiconductor materials then obtained in crystalline form are in a state making it difficult to work them and generally requiring, in order to have a satisfactory quality, a second passage through the solvent zone.
In addition, the electronic devices produced with these ternary or quaternary composite semiconductors require a precise ratio of the cadmium content to the mercury, the atomic fraction x of the cadmium having to be established e.g. at better than 0.5 atomic %. This precision also presupposes strict attention to the geometrical shape of the two initial alloy bars, i.e. a precise and careful machining thereof prior to their use.